It has become a hot topic of wireless cellular communication to integrate multi-hop capability by deploying relay stations (RS). For example, IEEE has established recently a relay workgroup in order to introduce RS into systems based on IEEE 802.16.
Currently, it is widely accepted that deploying RSs in wireless cellular systems can broaden coverage range, enhance the capacity of a cell, reduce the transmission power at the user station/mobile station (SS/MS) side, and prevent serious shielding. A feasible scheme is to organize a cellular system under the control of a base station (BS), in which all activities in the cell are under the common control of the BS, the BS sends signals to all SS/MSs and is responsible for answering the signaling requests from the SS/MSs.
However, the mode for transmitting signaling in current RSs is simplex; therefore, it is difficult to adjust a relay scheme according to practical conditions.